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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Simulation of oxygen isotopes and circulation in a late Carboniferous epicontinental sea with implications for proxy records
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Simulation of oxygen isotopes and circulation in a late Carboniferous epicontinental sea with implications for proxy records

机译：氧同位素和后期石炭系综合海洋循环的仿真，具有代理记录的影响

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Reconstructions of ancient ocean chemistry are largely based on geochemical proxies obtained from epicontinental seas. Mounting evidence suggests that these shallow inland seas were chemically distinct from the nearby open ocean, decoupling epicontinental records from broader ocean conditions. Here we use the isotope-enabled Community Earth System Model to evaluate the extent to which the oxygen isotopic composition of the late Carboniferous epicontinental sea, the North American Midcontinent Sea (NAMS), reflects the chemistry of its open-ocean sources and connect epicontinental isotope variability in the sea to large-scale ocean-atmosphere processes. Model results support estuarine-like circulation patterns demonstrated by past empirical studies and suggest that orographic runoff produced decreases in surface seawater delta O-18 (delta O-18(w)) of up to similar to 3 parts per thousand between the NAMS and the bordering ocean. Simulated sea surface temperatures are relatively constant across the sea and broadly reproduced from proxy-based delta O-18 paleotemperatures for which model-based values of epicontinental delta O-18(w) are used, indicating that offshore-onshore variability in surface proxy delta O-18 is primarily influenced by seawater freshening. Simulated bottom water temperatures in the NAMS are also reproduced from biogenic calcite delta O-18 using model-based values of epicontinental delta O-18, suggesting that benthic marine fossil delta O-18 is also influenced by seawater freshening and coastal upwelling. In addition, glacial-interglacial variations in nearshore seawater freshening counteract the effects of temperature on marine biogenic delta O-18 values, suggesting that salinity effects should be considered in delta O-18-based estimates of glacioeustatic sea level change from nearshore regions of the NAMS. Our results emphasize the importance of constraining epicontinental dynamics for interpretations of marine biogenic delta O-18 as proxies of paleotemperature, salinity, and glacioeustasy. (C) 2021 Elsevier B.V. All rights reserved.
机译：古代海洋化学的重建主要基于从陆表海获得的地球化学指标。越来越多的证据表明，这些内陆浅海在化学成分上与附近的公海不同，从而使陆表记录与更广泛的海洋条件脱钩。在这里，我们使用同位素支持的社区地球系统模型来评估晚石炭世陆表海北美中大陆海（NAMS）的氧同位素组成在多大程度上反映了其开放海洋源的化学性质，并将海洋中的陆表同位素变率与大规模海洋大气过程联系起来。模型结果支持过去的经验研究所证明的河口状环流模式，并表明地形径流在NAMS和毗邻海洋之间的表层海水delta O-18（delta O-18（w））中产生了高达千分之三的减少。模拟的海表面温度在整个海洋中相对恒定，并广泛地从基于代理的三角洲O-18古温度中复制，其中使用了基于模型的陆表三角洲O-18（w）值，这表明表面代理三角洲O-18的海-陆变化主要受海水更新的影响。利用基于模型的陆表三角洲O-18值，从生物成因方解石三角洲O-18重现了NAMS中的模拟底水温度，这表明底栖海洋化石三角洲O-18也受到海水更新和海岸上升流的影响。此外，近岸海水更新中的冰川间冰期变化抵消了温度对海洋生物成因三角洲O-18值的影响，这表明，在基于三角洲O-18的估算NAMS近岸地区冰川海平面变化时，应考虑盐度影响。我们的研究结果强调了限制陆表动力学对于解释海洋生物成因三角洲O-18作为古温度、盐度和冰川稳定性指标的重要性。（c）2021爱思唯尔B.V.保留所有权利。

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